MICROSCOPIC STRUCTURE OF HIGHER CRYPTOGAMIA. 



333- 



FIG. 212. 



commonest of all, F. vesiculosus (bladder-wrack), they are limited to 

 different invividuals. When a section is made through one of the flat- 

 tened receptacles of F. platycarpus, its interior is seen to be a nearly 

 globular cavity (Fig. 211), lined with filamentous cells, some of which are 

 greatly elongated, so as to 

 project through the pore 

 by which the cavity opens 

 on the surface. Among 

 these are to be distinguish- 

 ed, towards the period of 

 their maturity, certain fila- 

 ments (Fig. 212, A), whose 

 granular contents acquire 

 an orange hue, and gradu- 

 ally shape themselves into 

 oval bodies (B), each with 

 an orange-colored spot, and 

 two long thread-like appen- 

 dages, which, when dis- 

 charged by the rupture of 

 the containing cell, have 

 'for a time a rapid undula- 

 tory motion, whereby these 

 < antherozoids ' are diffused Antheridia and antherozoids of Fucus p i a tycar ? u S .-A,. 



through the Surrounding branching articulated hairs, detached frpm the walls of the 



lirmirl T^ino- ormVlcf flia receptacle, bearing antheridia in different stages of deve- 



iiqUlCl. -Lying amidst the lopn ^ en t; B, antherozoids, some of them free, others still 



filamentous maSS, near the included in their antheridial cells. 



walls of the cavity, are seen 



(Fig. 211) numerous dark pear-shaped bodies, which are the oogonia, or 

 parent-cells of the ' germ-cells/ Each of these oogonia gives origin, by 

 binary subdivision, to a cluster of eight germ-cells or oospheres, which is. 

 thence known as an 'octospore;' and these are liberated from their en- 

 velopes before the act of fertilization takes place. This act consists in 

 the swarming of the antherozoids over the surface of the oospheres, to. 

 which they communicate a rotatory motion by the vibration of their own 

 filaments. In the hermaphrodite Fuci it takes place within the recepta- 

 cles, so that the oospheres do not make their exit from the cavity until 

 after they have been fecundated; but in the monoecious and dioecious 

 species, each kind of receptacle separately discharges its contents, which 

 come into contact on their exterior. The antheridial cells are usually 

 ejected entire, but soon rupture so as to give exit to their filaments; 

 and the ( octospores ' separate into their component oospheres, which, 

 meeting with antherozoids, are fecundated by them. The fertilized oo- 

 spores soon acquire a new and firmer envelope; and, under favorable cir- 

 cumstances, they speedily begin to develop themselves into new plants. 

 The first change is the projection and narrowing of one end into a kind 

 of footstalk, by which the oospore attaches itself, its form passing from 

 the globular to the pear-shaped; a partition is speedily observable in^its 

 interior, its single cell being subdivided into two; and by a continuation 

 of a like process of duplication, first a filament and then a frondose ex- 

 pansion is produced, which gradually evolves itself into the likeness of 

 the parent plant. 



-329. The whole of this process may be watched without difficulty, by 

 obtaining specimens of F. vesiculosus at the period at which the fructifi- 

 cation is shown to be mature by the recent discharge of the contents of" 



